The one that lies only has a 1 in 10 chance of making up a number that will pass the check! Cool shortcut: If it starts with a 1, 2, 7, 8, or 9, they're lying. Those are reserved for things that aren't credit cards 👍
29
Default Username - 4day
But you only can ask one question and asking for their CC information won't help you find the exit.
16
JackbyDev - 3day
Did you not read the comic?
3
Default Username - 3day
You make a good point there...
2
Wirlocke - 3day
I thought credit card numbers were just for credit cards, what are the "things that aren't credit cards"?
Genuine question I'm just curious.
1
Riskable - 2day
1,2: Airline cards (e.g. Lufthansa)
7: Gas cards (Shell, Mobile)
8: Health-related and telecom cards (remember those old Sprint calling cards? That)
9: Reserved.
3,4,5, and 6 are the only types that would count as "credit cards".
2
Wirlocke - 2day
Interesting!
2
Dagnet @lemmy.world - 4day
This kinda falls apart with the knights talking at the start. Either there is 1 that only tells truth with the other not being bound by those rules or one that only tells lies with the other one doing whatever since one of those 2 is telling a lie.
24
Cris - 4day
That's a good point actually, they kinda messed that part up a bit
16
Sophienomenal - 3day
For those interested, ignoring the contradictory presentation of the riddle (as the knights themselves would not say the riddle since one always lies and one always tells the truth), the solution is simple. Ask the knights what the other knight would answer when asked what door is correct, and they will both say which path not to go to. Thus you pick the path that neither Knight says!
Logic:
Liar: Will say the wrong option, as they're being asked which door the truth telling knight would say (and they will lie about what the truth-teller would say)
------------------------------------------
Truth-teller: Will say the wrong option, as they're being asked which door the liar would say (and they'll tell the truth about that)
NOTE: This can be expanded to a case with n doors by asking the knights to provide all the options that the other knight could say, and each will provide n-1 options, so you'd pick the one option that neither knight says. It is possible the liar may not list all options, but the truth-teller would, so the problem could still be worked out regardless (and you'd know which knight is the liar in that case).
9
Cris - 3day
Nice work!
2
PrivateNoob - 4day
The easiest solution is to ask what is the color of their capes that they are wearing
4
ArachnidMania @lemmy.ca - 3day
You've then found out which one lies, but you've used up your one question and now don't know what is the correct door to leave.
6
PrivateNoob - 3day
Oh shit that's true
3
petersr @lemmy.world - 3day
Am I mistaken for recalling that in the original riddle, the question should have a boolean outcome (yes/no)?
Having a question with a big domain makes it a lot easier to guess what is a false and true outcome.
Cris_Color in femcelmemes
mimi rule (crosspost)
Oooh! This is a great solution to this problem! Just write down both numbers and perform a luhn check:
https://en.wikipedia.org/wiki/Luhn_algorithm
The one that lies only has a 1 in 10 chance of making up a number that will pass the check! Cool shortcut: If it starts with a 1, 2, 7, 8, or 9, they're lying. Those are reserved for things that aren't credit cards 👍
But you only can ask one question and asking for their CC information won't help you find the exit.
Did you not read the comic?
You make a good point there...
I thought credit card numbers were just for credit cards, what are the "things that aren't credit cards"? Genuine question I'm just curious.
1,2: Airline cards (e.g. Lufthansa)
7: Gas cards (Shell, Mobile)
8: Health-related and telecom cards (remember those old Sprint calling cards? That)
9: Reserved.
3,4,5, and 6 are the only types that would count as "credit cards".
Interesting!
This kinda falls apart with the knights talking at the start. Either there is 1 that only tells truth with the other not being bound by those rules or one that only tells lies with the other one doing whatever since one of those 2 is telling a lie.
That's a good point actually, they kinda messed that part up a bit
For those interested, ignoring the contradictory presentation of the riddle (as the knights themselves would not say the riddle since one always lies and one always tells the truth), the solution is simple. Ask the knights what the other knight would answer when asked what door is correct, and they will both say which path not to go to. Thus you pick the path that neither Knight says!
Logic:
NOTE: This can be expanded to a case with
ndoors by asking the knights to provide all the options that the other knight could say, and each will providen-1options, so you'd pick the one option that neither knight says. It is possible the liar may not list all options, but the truth-teller would, so the problem could still be worked out regardless (and you'd know which knight is the liar in that case).Nice work!
The easiest solution is to ask what is the color of their capes that they are wearing
You've then found out which one lies, but you've used up your one question and now don't know what is the correct door to leave.
Oh shit that's true
Am I mistaken for recalling that in the original riddle, the question should have a boolean outcome (yes/no)?
Having a question with a big domain makes it a lot easier to guess what is a false and true outcome.